the r-commands (rsh, rlogin, rcp, rexec)
termsecurityIT support
The Berkeley remote-access family - rlogin for a shell, rsh to run one command, rcp to copy files, rexec to execute with a password - that ran the Unix world before SSH, authenticating on trust files (.rhosts, hosts.equiv) that said, in effect, this machine vouches for that machine.
Everything travelled in the clear, and the trust was based on source IP address and hostname, both forgeable. A single compromised host with a permissive .rhosts could cascade through an entire cluster - which is precisely how the Morris worm and a generation of intrusions moved laterally. SSH exists because of these tools, replaced them command for command, and their retirement is the canonical example of an entire protocol family removed rather than patched.
Also known as: rsh, rlogin, rcp, rexec, rhosts, berkeley r commands